The present invention relates to a controlled-release oral preparation comprising esculetin or its derivative as an effective component.
Because the controlled-release oral preparation of the present invention can gradually release esculetin or its derivative in a controlled manner over a long period of time, the preparation can maintain the effect of the esculetin or the derivative for a long time by a single administration. As a result, the preparation can improve symptoms such as inflammations, aches, performance disorders, and the like which are induced by a break-down of arthrodial cartilage such as osteoarthropathy, chronic rheumatism, etc.
Chronic rheumatism, rheumatic fever, osteoarthropathy, and the like are included in the arthropathy. Of these chronic rheumatism and osteoarthropathy are suffered by a great number of patients and thus are considered to be major arthropathy. There are two types of osteoarthropathy; one is congenitus or secondary in nature, and the other is primary and induced by progressive deformation of arthrodial cartilage due to aging. The number of patients suffering from the primary osteoarthropathy has been increasing in recent years as the number of aged people increases. There is a significant difference between the cause of disease and pathology of chronic rheumatism and those of osteoarthropathy. However, these diseases are common inasmuch as the ultimately obstruct joint functions by fracture of the arthrodial cartilage. A primarily chosen medicine for rheumatic diseases such as chronicrheumatism, rheumatic fever, systemic lupus erythematosus, osteoarthropathy, and the like is an analgesicanti-inflammatory agent such as aspirin, indomethacin, or the like. In addition to these medicines, gold preparations such as thiosol, immunomodulating drug, steroid drugs, D-penicillamine, and the like are used as a chronic arthropathy curative medicine. On the other hand, esculetins such as esculetin, 4-methylesculetin and the like are known as medicines possessing a cholesterol reducing effect, vascular reinforcing effect, and anti-oxidation effect (Japanese Patent Publication No. 16626/1967). Carboxylic acid diesters of 4-methyl esculetin having 6-25 carbon atoms, particularly caprylic acid diester lauric acid diester, and palmitic acid diester, are known to exhibit an anti-inflammatory effect (French Patent No. 2276819).
The above conventional analgesic antiinflammation agents not only exhibit no effect of depressing fractures of the arthrodial cartilage, but also some of these agents have been confirmed to have an effect of exacerbating the diseases in an experiment using cartilage cells. Furthermore, no fracture depressant effect of the arthrodial cartilage has been clinically found in the above curative medicines for chronic arthropathy and osteoarthropathy. The arthrodial cartilage consists of cartilage cells and a cartilage matrix. The cartilage matrix has a three-dimensional matrix structure wherein type II collagen which is a cartilage cell-producing fibrous protein and proteoglycan which is a protein polysaccharide composite material, are non-conjunctively bonded and intertwined with hyaluronic acid in a complex manner. The cartilage matrix contains a large quantity of water which contributes to maintaining a normal joint function. The major polysaccharide forming proteoglycan is glycosaminoglycan consisting of chondroitin sulfate and keratan sulfate.
Watanabe et al. found that esculetins such as esculetin, 4-methyl esculetin, and the like strongly depress a decrease in the amount of glycosaminoglycan in the matrix due to stimulation of interleukin-1 and the like, and thus are useful as a protective agent for the arthrodial cartilage. (Japanese Patent Application Laid-open No. 312925/1994).
When orally-administered, these esculetins are immediately metabolized: in the liver and found in blood as a conjugate with glucuronic acid or sulfuric acid. The glucuronic acid conjugate is considered to become esculetin in the arthrodial cartilage and exhibit a cartilage protection effect. However, because the glucuronic acid conjugate has high water solubility and is immediately eliminated from the kidney, there is almost no such substance present in the blood three hours after oral administration. It is necessary for esculetin or a derivative thereof to be continuously present in the cartilage for a long time at a concentration above a certain level (0.01-100, preferably 0.1-10 ng/mg of cartilage) to exhibit the cartilage protection effect, requiring the administration of a large amount of the medicine (200-1,000 mg/kg) several times (6-12 times) a day. Administration of a large amount of the medicine involves a rapid increase in the blood concentration, thereby increasing risks of side effects.
In order to solve these problems, the inventors of the present invention have conducted extensive studies and found that it is possible to continuously maintain the concentration required for the compound to locally exhibit the medical effect (0.01-100, preferably0.1-10ng/mg of cartilage) for a long period of time (10 hours or more) and to reduce side effects at a lower dose than conventional medicines for oral administration by controlling release of esculetin or its derivative from a preparation.
Accordingly, an object of the present invention is to provide a novel arthropathy therapeutic oral preparation comprising esculetin or its derivative which can continuously maintain the local concentration of the effective components by controlled release, even if administered at a small dose, thereby decreasing a risk of side effect.
The present invention has been accomplished to solve these problems and relates to a controlled-release oral preparation such as granules, tablets, capsules, etc. comprising esculetin its derivative, or pharmacologically acceptable salts thereof, which can release the effective components (major medicines esculetin and its derivative) in a controlled manner.
The medicinal effect of esculetin or its derivatives has a correlation with the intracartilaginous concentration of esculetin or its derivatives after administration, esculetin: metabolized from the derivatives, and glucuronic acid conjugates of esculetins which produce esculetin by decomposition with time.
The intracartilaginous concentration of esculetin or its derivatives after administration, esculetin metabolized from the derivatives, and glucuronic acid conjugates of esculetins which produce esculetin by decomposition with time has a correlation with the sum of the blood concentration of esculetin or its derivatives and glucuronic acid conjugates of esculetin or its derivatives. When the sum of: intracartilaginous concentration of esculetin or its derivatives is 0.01 ng/mg of cartilage, the sum of blood concentration of esculetin or its derivatives and 6-position or 7-position glucuronic acid conjugates of esculetin or its derivatives which release esculetin or its derivatives in the cartilage is about 0.5 xcexcmol/L. Therefore, to maintain the medicinal effect of esculetin or its derivatives, the sum of the blood concentration of esculetin or its derivatives and 6-position or 7-position glucuronic acid conjugates of esculetin or its derivatives which release esculetin or its derivatives in the cartilage must be 0.5 xcexcmol/L or more.
Because of the above reasons, there are no limitations to the form and formulation for the oral administration preparation of the present invention inasmuch as the preparation comprises esculetin, its derivatives, or pharmacologicalIly acceptable salts thereof as major components, can be orally administered, and, when orally administered to a dog at a dose of 1 to 100 mg/kg, can maintain the blood concentration of 0.5 xcexcmol/L or more of esculetin or its derivatives and 6-position or 7-position glucuronic acid conjugates of esculetin or its derivatives which release esculetin or its derivatives, in the cartilage for a period of 10 hours or more.
The esculetin, its derivatives, or the pharmaceutically acceptable salts thereof used as an effective component in the present invention is a compound known in the art and represented by the following formula (I) (Japanese Patent Application Laid-open No. 312925/1994). 
wherein R1 and R2 are individually a hydrogen atom or a saturated or unsaturated aliphatic acyl group having 2-25 carbon atoms or benzoyl group, and R3 is a hydrogen atom, hydroxyl group, alkyl group, aryl group, or aralkyl group.
Hydrogen atom, acetyl group, pivaloyl group, capryloyl group, lauroyl group, palmitoyl group, stearoyl group, linoleoyl group, docosahexaenoyl group, and benzoyl group are given as preferable examples of the groups R1 and R2 in the formula. (I)
The alkyl group represented by R3 in the above formula (I) is preferably an aliphatic alkyl group, and more preferably a lower alkyl group having 1-4 carbon atoms, such as a methyl group; ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, and t-butyl group. Of these, a methyl group and ethyl group are particularly preferable. The aryl group represented by R3 in the above formula (I) is preferably an aryl group having 6-12 carbon atoms such as a phenyl group, naphthyl group, or biphenyl group. One or more hydrogen atoms in these aryl groups may be replaced by a lower alkyl group having 1-4 carbon atoms, halogen atom, or hydroxyl group. The aralkyl group represented by R3 in the above formula (I) is preferably a lower alkyl group having 1-4 carbon atoms substituted by an aryl group having 6-12 carbon atoms such as, for example, a benzyl group, phenylethyl group, phenylpropyl group, and phenylbutyl group. One or more hydrogen atoms on the aryl group of these aralkyl groups may be replaced by, for example, a lower alkyl group having 1-4 carbon atoms, halogen atom, or hydroxyl group.
The pharmaceutically acceptable salt of an esculetin derivative of the present invention is formed with a hydroxyl group at the 6 or 7 position. Salts with an inorganic base or organic base are included in the pharmaceutically acceptable salt. Hydroxides, carbonates, bicarbonates, and the like of ammonium, potassium, sodium, lithium, calcium, magnesium, or aluminum, for example, are given as the inorganic base suitable for forming these salts.
As examples of the organic base, a salt of mono-, di-, or tri-alkylamine such as methylamine, dimethylamine, and triethylamine, salt of mono-, di-, or tri-hydroxyalkylamine, guanidine salt, N-methylglycosamine salt, amino acid salt, and the like can be given.
Esculetin is commercially available and its derivatives can be manufactured by a method described in the above-mentioned laid-open Patent Application.
Preferable esculetin and esculetin derivatives used in the present invention are as:follows: esculetin, 4-methylesculetin, 4-ethylesculetin, 4-(n-propyl) -esculetin, 4-(isopropyl)-esculetin, 4-(n-butyl)-esculetin, 4-(s-butyl)-esculetin, 4-(t-butyl)-esculetin, 4-(isobutyl)-esculetin, 4-methylesculetin 6,7-bis(acetate), 4-methylesculetin 6,7-bis(stearate), 4-methylesculetin 6,7-bis(linolate), 4-methylesculetin 6,7-bis(docosahexaenoate), esculetin 6,7-bis(benzoate), 4-methylesculetin 6,7-bis(benzoate), methylesculetin 6,7-bisacetate, esculetin 6,7-bis(pivalate), and esculetin 6-monopivalate.
These compounds induced no deaths or exhibited no conspicuous toxicity when a suspension in a 0.5% methyl cellulose aqueous solution was intraperitoneally administered to Crj: CD-1 (ICR) male mice (age: six weeks, five mice per group) once a day for four consecutive days.
Furthermore, a culture broth obtained by culturing a mixture of cartilage cells aseptically extracted from the. articulation genus cartilage of rabbits, a cartilage fracture factor (forbolmyristate acetate), and the above compounds exhibited a remarkable suppression of a decrease in the amount of glycosaminoglycan which constitutes the cartilage matrix, confirming that these compounds have an effect of depressing arthrodial cartilage fracture.
In addition, in an experiment comprising extracting the cartilage from the head of femur of an SD-series male rat, aseptically embedding the extracted cartilage into the shaved back of a BALB/C female mouse, administering the above compounds to the mouse, and measuring proteoglycan constituting the cartilage matrix in the head of femur, it was found that a decrease in the amount of the proteoglycan was suppressed, indicating that these compounds have an effect of depressing arthrodial cartilage fracture.
The period of time required for the oral administration preparation of the present invention comprising esculetin, its derivative, or a pharmaceutically acceptable salt thereof as a main component to dissolve 80% of the main component-was between 0.5 and 23 hours, when evaluated by the dissolution test according to the paddle method of the Japanese Pharmacopoeia (paddle rotation: 100 rpm, test solution: purified water, test solution temperature: 37xc2x0 C.). For the preparation of the present invention to maintain the blood concentration, in terms of the sum of the concentration of esculetin or its derivatives and the concentration of 6-position or 7-position glucuronic acid, conjugates of esculetin or its derivatives which release esculetin or its derivatives in the cartilage, of 0.5 xcexcmol/L or more, when 1 to 100 mg/kg of the preparation is administered to a dog, the period of time required for the preparation to dissolve 80% of the main component as determined according to the above dissolution test method must be 0.5 to 23 hours. Such a preparation is preferably in the form of granules, tablets, or capsules into which the granules are filled.
The amount of esculetin or its derivative in the preparation is usually from 1-99 wt % (hereinafter indicated simply by xe2x80x9c%xe2x80x9d), preferably from 5-70%, and more preferably from 10 to 40%.
The granules are prepared by mixing esculetin, its derivative, or a pharmaceutically acceptable salt thereof, a base component for controlling release of the active component, an excipient, binder, disintegrator, and the like, and granulating the mixture by a known granulation method. Either the dry granulating method or wet granulation method is applicable.
A method of using a slug machine and a method of using a roller compactor are given as the dry granulating method. A wet screening method, rolling granulation method, and pulverization granulation method are given as examples of the wet granulation method. As required, the release control action of the granules may be adjusted by providing the granules with a coating. The-release control action of the granules may also be adjusted by producing granules by mixing esculetin, its derivative, or a pharmaceutically acceptable salt thereof, and additives commonly used for the preparation of granules such as an excipient, binder, disintegrator, and the like, and coating the granules with an enteric coating base, an insoluble coating base, or the like.
The tablets are prepared by mixing esculetin, its derivative, or a pharmaceutically acceptable salt thereof, a base component for controlling release of the active component, an excipivent, binder, disintegrator, and the like, granulating the mixture by a known granulation method, and tabletting the granules after the addition of a lubricant. The tablets are also prepared by mixing esculetin, its derivative, or a pharmaceutically acceptable salt thereof, a base component for controlling release of the active component, an excipient binder, disintegrator, and the like, then directly tabletting the mixture with the addition of a lubricant.
Either the dry granulating method or wet granulation method is applicable to the preparation of granules for tabletting. A method of using a slug machine and a method of using a roller compactor are given as the dry granulating method. An extrusion granulation method, rolling granulation method, and pulverization granulation method are given as examples of the wet granulation method.
As required, the release control action of the tablets may be adjusted by providing the tablets with a coating. The release control action of the tablets may also be adjusted by producing tablets from esculetin, its derivative, or a pharmaceutically acceptable salt thereof, and additives commonly used for the preparation of tablets, and providing the tablets with a coating of an enteric coating base, an insoluble coating base, or the like.
The capsules are prepared by mixing esculetin, its derivative, or a pharmaceutically acceptable salt thereof, a base component for controlling release of the active component, an excipient, binder, disintegrator, and the like, and granulating the mixture by a known granulation method, and filling the granules into capsules. Any of gelatine capsules, hydroxypropylmethylcellulose capsules, hydroxypropylmethylcellulose acetate succinate capsules may be used for the preparation of the capsules.
As required, the release control action of the capsules may be adjusted by providing the capsules with a coating. The release control action of the capsules may also be adjusted by producing granules from esculetin, its derivative, or a pharmaceutically acceptable salt thereof, and additives commonly used for the preparation of granules, filling the granules into capsules, and providing the capsules with a coating of an enteric coating base, an insoluble coating base, or the like.
The base material used for the release control is preferably a gel-forming polymer base.
As the gel-forming polymer base, carmellose sodium, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, and hydroxypropylmethylcellulose are preferable. Of these, hydroxypropylmethylcellulosel is particularly preferable. As hydroxypropylmethylcellulose, hydroxypropylmethylcellulose 2910, hydroxypropylmethylcellulose 2208, and hydroxypropylmethylcellulose 2906 are preferable.
Although the amount of the gel-forming polymer base to be added varies according to the properties and amount of esculetin, its derivative, or the pharmacologically acceptable salt, the properties and molecular weight of the gel-forming polymer base, the types and amount of other additives, and the type of the preparation, the addition in the amount of 0.5-90%, preferably 10-70%, and more preferably 35-70% can ensure that the resulting preparation elutes 80% of esculetin or its derivative in a period of 0.5 to 23 hours, thereby enabling the preparation to maintain the target blood concentration.
Known excipients, binders, disintegrators, and lubricants can be used for the preparation. Crystalline cellulose/starch, lactose, and the like can be given as examples of vehicles. As examples of binders, hydroxypropylcellulose, polyvinyl alcohol, polyvinyl pyrrolidone, and the like can be given. As examples of disintegrators, low-substituted hydroxypropylcellulose, croscarmellose sodium, crospovidone, and the like can be given. As lubricants, talc, magnesium stearate, and the like can be given. Other additives such as a coloring agent, perfume, stabilizer, preservative, taste improver, antioxidant, and the like may be added as required.
When controlling release of the active component from granules by coating or to provide the preparation with a release control effect, an enteric coating base or an insoluble coating base is preferably used.
Hydroxypropylmethylcellulose acetate succinate, hydroxypropylmethylcellulose phthalate, cellulose acetate phthalate, carboxymethylethylcellulose, methacrylic acid copolymer L, and methacrylic acid copolymer S are preferably used as the enteric coating base. Of these, hydroxypropylmethylcellulose acetate succinate and hydroxypropylmethylcellulose phthalate are particularly preferable.
As the insoluble coating base, ethyl cellulose and aminoalkylmethacrylate copolymer RS are preferable, with the former being more preferred.
A known coating apparatus can be used for the enteric coating or insoluble coating. A fluidized bed granulator, a centrifugal granulation coating apparatus, and the like can be given.
Although the amount of the enteric coating base (coating ratio) varies according to the form and formulation of the preparation, the type, properties, and molecular weight of the coating base, the period of time for which dissolution is controlled, and the like, about 0.5-50%, and preferably about 1-20% of the total weight of the preparation is used.
The insoluble coating operation is performed using a mixture of an insoluble coating base anda suitable water-soluble coating base. Hydroxypropylmethylcellulose 2910 is given as an example of the water-soluble coating base. Although the ratio of the insoluble coating base and water-soluble coating base varies according to the form and formulation of the preparation; and the type, properties, and molecular weight of the coating base, the period of time for which dissolution is controlled, and the like, the ratio of about 1:10 to 10:1, and preferably about 3:7 to 7:3, is applied. The coating ratio is about 0.5 to 50%, and preferably about 1-20 of the weight of the granules.
It is particularly preferable that the preparation of the present invention comprises 0.5 to 90% of a gel-forming polymer base and 0.5 to 50% of an enteric coating base and/or an insoluble coating base.
The present invention will be described in more detail by way of examples.
However, these examples should not be construed as limiting the present invention.